Balanus crenatus

Balanus crenatus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Thecostraca
Subclass:	Cirripedia
Order:	Balanomorpha
Family:	Balanidae
Genus:	Balanus
Species:	B. crenatus
Binomial name
Balanus crenatus Bruguière, 1789
Subspecies[1]
B. c. crenatus B. c. curviscutum B. c. delicatus

Balanus crenatus is a species of acorn barnacle in the Balanidae family. It is found in the North Pacific and the North Atlantic Ocean.

Description

The shell of B. crenatus is made of six calcareous plates and grows up to 25 millimetres (0.98 in) across. The upper edge of the plates are toothed and the shell is often tilted to one side. The opercular aperture is diamond shaped and protected by two further plates which can slide across when the animal is not feeding.[2]

Distribution

This is a boreal species distributed in intertidal and sublittoral zones of the North Pacific and the North Atlantic. It has a similar distribution to Balanus balanus, a species with which it is often associated.[3]

Biology

This barnacle is a hermaphrodite and the reproductive organs develop during the winter. Individuals in a group fertilise each other and, after a period of maturation, nauplii are liberated into the water. After a number of moults, the larvae settle out of the zooplankton in about April and attach themselves to rocks and stones on the sea floor. B. crenatus is a fast-growing barnacle and can grow from a length of 3 millimetres (0.12 in) to 9 mm (0.35 in) in the month of May after settling. It is fully grown by August and ready to reproduce in its first winter.[4]

Ecology

This species is mainly found in the sublittoral zone but can sometimes be found under stones or overhangs on the lower shore. It colonises pebbles, bedrock, shells and artificial structures. It is found in both calm and exposed waters and can tolerate low salinity levels [2] and is found at depths of up to 60 metres (200 ft). It seems to favour habitats with strong currents and when overcrowding occurs, may be distorted to fit the space available. It is often found growing alongside another species of barnacle, Balanus balanus.[4]

The main predator is the juvenile common starfish (Asterias rubens). Medium sized barnacles seem to be at greatest risk. Small specimens are ignored while large specimens seem able to withstand attack but in some years, the population is decimated.[5]

References

1. WoRMS (2011). "Balanus crenatus". World Register of Marine Species. Archived from the original on 28 April 2011. Retrieved May 5, 2011.
2. Nicola White (2004). "Balanus crenatus. An acorn barnacle". Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Plymouth: Marine Biological Association of the United Kingdom. Retrieved May 5, 2011.
3. Francis Kerckhof (2002). "Barnacles (Cirripedia, Balanomorpha) in Belgian waters, an overview of the species and recent evolutions, with emphasis on exotic species" (PDF). Bulletin van het Koninklijk Belgisch Instituut voor Natuurwetenschappen. Biologie. 72 (Suppl): 93–104.
4. H. Barnes & Margaret Barnes (1954). "The general biology of Balanus balanus (L.) Da Costa". Oikos. 5 (1): 63–76. doi:10.2307/3564651. JSTOR 3564651.
5. H. Barnes & H. T. Powell (1951). "The growth rate of juvenile Asterias rubens L." (PDF). Journal of the Marine Biological Association of the United Kingdom. 30 (2): 381–385. doi:10.1017/S0025315400012844. Archived from the original (PDF) on 2011-08-26.